The present invention generally relates to a vacuum lamination apparatus and a vacuum lamination method. In particular, the present invention relates to a vacuum lamination apparatus and a vacuum lamination method of applying a vacuum lamination process to a member to be laminated such as a component of a solar cell module.
A large amount of fossil fuel has been consumed since Industrial Revolution, and the global environment has been worsened due to air pollution and global warming by CO2. Accordingly, in recent years, environmental consciousness has been increased in the global scale. In this circumstance, solar cells have been expected to be as safe, easy to handle, and clean energy source. There are several types of solar cells including a single crystal silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, and a compound semiconductor solar cell. Among these types of solar cells, the amorphous silicon solar cell can be a flexible and large area solar cell with relatively low cost, thereby increasing applications. In general, the solar cell module is exposed to open air. Accordingly, it is necessary to improve durability against temperature, humidity and external pressure for a reliable device. One of techniques to meet the requirement is a vacuum lamination process.
FIGS. 16(A) and 16(B) are schematic views of a conventional vacuum lamination apparatus, in which FIG. 16(A) is a perspective view thereof, and FIG. 16(B) is a sectional view taken along line 16(B)-16(B) in FIG. 16(A). The conventional vacuum lamination apparatus comprises a base plate 1001, a tube 1003 arranged on the base plate in a ring shape and having evacuation holes 1002 in an inside wall thereof, and a vacuum pump 1008. The tube 1003 is fixed onto the base plate 1001 with a fixing material 1004. A cover sheet 1005 entirely covering the tube 1003 with the ring shape forms a processing space 1006 for the lamination process.
In the vacuum lamination process, first, a solar cell module component 1007 with a sheet shape constituting a solar cell module is placed in the vacuum lamination apparatus. Then, the vacuum pump 1008 exhausts air between materials in a degassing process. The materials are heated up to a temperature at which a sealant material contained in the solar cell module component can be cross-linked or cured, and held at the temperature for a predetermined time until the sealant material is fully cured. After that, the materials are cooled down and the vacuum pump is stopped, thereby returning to the atmospheric pressure.
FIG. 17 is a schematic view of a solar cell module manufactured by the vacuum lamination apparatus. A thermo-adhesive sealant material 1011 and a top surface covering member (surface protection film) 1012 are sequentially formed on a front surface of a photovoltaic element 1010. A thermo-adhesive sealant material 1013 and a rear surface reinforcing member 1014 are sequentially formed on a rear surface of the photovoltaic element 1010.
In the conventional vacuum lamination apparatus shown in FIGS. 16(A) and 16(B), the cover sheet 1005 bends at an acute angle at a contact part with the tube in the vacuum process. When the operation continues in such a state, it is possible to generate a crack at the contact part of the cover sheet 1005 due to long term temperature stress. A leakage may lead to insufficient degassing of the materials of the solar cell module component 1007, thereby generating an air bubble in the solar cell module and causing an external appearance defect.
To solve this problem, Japanese Patent Publication (Kokai) No. 09-051111 has disclosed a technique (paragraphs 0025-0026 and FIG. 5), in which a buffer member is disposed along inside a tube to eliminate an acute angle bending portion of the cover sheet. FIG. 18 is a schematic sectional view of a conventional vacuum lamination apparatus having the buffer member disposed along inside the tube.
A solar cell module component 1020 is sandwiched between filler flow preventing materials 1026 for preventing a flow of a filler material filled in a surrounding space, and is placed on a base plate 1021 through a net 1022 for forming an air flow path. A buffer member 1024 with an L cross section is disposed along inside the tube 1023 as shown in FIG. 18. A cover sheet 1025 covers the whole tube 1023, and degassing is conducted.
In the conventional vacuum lamination apparatus shown in FIGS. 16(A) and 16(B) or FIG. 18, when the vacuum lamination apparatus is scaled-up to handle a large solar cell module, it is necessary to increase rigidity of the apparatus as a whole by increasing adhesion between the base plate and the tube. However, even if the base plate and the tube are firmly integrated together with welding, it is difficult to obtain sufficient rigidity of the apparatus as a whole as a tube shape member generally does not provide high rigidity.
Further, it is necessary to provide a buffer member for protecting the cover sheet, so that the numbers of parts and manufacturing steps increase, thereby increasing cost of the apparatus. Also, it is difficult to form a large number of the exhaust holes in the tube, thereby deteriorating evacuation performance.
In view of the problems described above, the present invention has been made, and an object of the present invention is to provide a vacuum lamination apparatus for manufacturing a solar cell module with low cost and high productivity.
Another object of the invention is to provide a vacuum lamination method for manufacturing a solar cell module with low cost and high productivity.
A further object of the invention is to provide a vacuum lamination apparatus for performing a high quality lamination process in which a cover sheet is securely sealed to suppress air leakage.
Further objects and advantages of the present invention will be apparent from the following description of the invention.